Displaced wafer detection systems

ABSTRACT

A displaced wafer detection system comprises a unified pod, a pod opener, a horizontal transmission robot, and a sensor. The unified pod encloses a plurality of wafers in a first position. The pod opener opens the unified pod. The horizontal transmission robot carries the wafers from the unified pod to a second position. When one of the wafers reaches the second position, the sensor detects if any wafer slips during wafer transmission from the unified pod.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor manufacturing techniques,and more particularly to displaced wafer detection systems.

2. Description of the Related Art

A unified pod, such as a front opening unified pod (FOUP) packing 13 or25 pieces of 12″ wafers, is utilized to transport wafers betweenfabrication steps and prevents contamination of wafers. When a unifiedpod is sent to a pod opener, the pod opener automatically opens the doorof the unified pod, and the wafers therein are acquired by othermechanisms and sent to various fabrication equipment.

FIG. 1 is a fab floor plan. When unified pod 10 is sent to pod opener20, pod opener 20 automatically opens the door of unified pod 10.Horizontal transmission robot 30 comprises robot arms R1 and R2.Horizontal transmission robot 30 utilizes robot arm R1 to carry a waferlot in a horizontal direction from unified pod 10 to another position.As shown in FIG. 2, the wafers remain substantially parallel. Normally,all the acquired wafers are intended to substantially reach the sameposition of wafer 12 in the floor plan of FIG. 2, i.e. the centers ofthe wafers are intended to lie on substantially the same line. Somewafers, such as wafer 11, however, may fall occasionally, e.g. thecenter of wafer 11 does not lie on the same line as other wafers.

When horizontal transmission robot 30 rotates to an orientation as shownin FIG. 3, the wafers are transferred from horizontal transmission robot30 to vertical transmission robot 40, wherein the wafers remainparallel, and the wafer 11 is still incorrectly displaced. Verticaltransmission robot 40 vertically rotates to make the wafers stand in avertical orientation. Normally, when the wafers stand in the verticalorientation, transporter 50 is intended to move upward from its originalposition below vertical transmission robot 40 to support the wafersstill in the vertical orientation, and moves the wafers along a specifictrack. As shown in FIG. 4, because wafer 11 is carried at an incorrectposition by vertical transmission robot 40, wafer 11 may fall ontransporter 50 during rotation of vertical transmission robot 40, whichis called a wafer drop. While transporter 50 is moving upward from itsoriginal position below vertical transmission robot 40 to support thewafers, the wafer 11 thereon will cause support of the wafer by thetransporter 50 to fail and even lead to collapse of all the wafers.

BRIEF SUMMARY OF THE INVENTION

An exemplary embodiment of a displaced wafer detection system comprisesa unified pod, a pod opener, a horizontal transmission robot, and asensor. The unified pod encloses a plurality of wafers in a firstposition. The pod opener opens the unified pod. The horizontaltransmission robot carries the wafers from the unified pod to a secondposition. When one of the wafers has reached the second position, thesensor detects if any wafer slips during wafer transmission from theunified pod.

An exemplary embodiment of a displaced wafer detection system comprisesa unified pod, a pod opener, a horizontal transmission robot, a verticaltransmission robot, a transporter, and a sensor. The unified podencloses a first lot of wafers in a first position. The pod opener opensthe unified pod. The horizontal transmission robot carries the wafersfrom the unified pod. The vertical transmission robot, when in a firstorientation, acquires the wafers and then vertically rotates to a secondorientation. The transporter moves upward to support the wafers in avertical orientation when the vertical transmission robot is in thesecond orientation. The sensor detects if any wafers have dropped fromthe vertical transmission robot before the wafers are supported by thetransporter.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a schematic diagram of a fab;

FIG. 2 is a schematic view of a horizontal transmission robot acquiringa wafer lot;

FIG. 3 is a schematic view of a vertical transmission robot acquiring awafer lot;

FIG. 4 is a schematic diagram of a wafer dropping from the verticaltransmission robot;

FIG. 5 is a schematic diagram of a displaced wafer detection system;

FIG. 6 is a schematic diagram of the arrangement of transmitters andreceivers of a sensor;

FIG. 7 is a schematic diagram of the arrangement of transmitters andreceivers of another sensor;

FIG. 8 is a side view of a sensor in a first direction;

FIG. 9 is a side view of a sensor in a second direction; and

FIG. 10 is a side view of an exemplary sensor.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

In a floor plan of fab 100A in FIG. 5, sensor 60 is disposed betweenhorizontal transmission robot 30 and pod opener 20, and sensor 70 isdisposed between vertical transmission robot 40 and transporter 50.Control unit 1 which may be integrated in or coupled to a manufacturingexecution system (MES) dominates sensors 60 and 70 and receivesdetection data therefrom. Unified pod 10 encloses a plurality of wafers13. When unified pod 10 is sent to pod opener 20, pod opener 20automatically opens the door of unified pod 10, wherein wafers 13 aresubstantially parallel and in a first position. The centers of wafers 13in the opened unified pod 10 lie substantially on a first line.

Horizontal transmission robot 30 comprises robot arms R1 and R2.Horizontal transmission robot 30 utilizes robot arm R1 to horizontallycarry wafers 13 from unified pod 10 to a second position, wherein wafers13 remain substantially parallel. When no wafer slips while beingcarried from unified pod 10, the centers of wafers 13 reach and lie on asecond line. When one of the wafers has reached the second position,sensor 60 detects if any wafers slipped during transport of wafers 13from unified pod 10 to the second position by horizontal transmissionrobot 30. Sensor 60 is disposed between horizontal transmission robotand the pod opener while wafers 13 are carried by horizontaltransmission robot 30 from unified pod 10 to the second position. Sensor60 may be fixed to pod opener 20 or horizontal transmission robot 30, oreven to another movable or stationary equipment or object. For example,sensor 60 is fixed to a first surface of pod opener 20, facinghorizontal transmission robot 30 while horizontal transmission robot 30is carrying wafers 13 from unified pod 10.

Sensor 60 comprises at least one transmitter dispatching a signal andone receiver accepting the signal. The transmitter and the receiver maybe disposed on a third line parallel to the second line, wherebydetection signals are transmitted from the transmitter to the receiveralong the third line. The path of the detection signals liessubstantially on the same plane as the first and the second lines.Control unit 1 may direct the transmitter to deliver detection signalswhen horizontal transmission robot 30 has delivered wafers 13 fromunified pod 10 to the second position. Control unit 1 determines that atleast one of wafers 13 slips when one of wafers 13 has reached thesecond position when the receiver does not receive the delivereddetection signals. Control unit 1 stops horizontal transmission robot30. The detection signals are preferably implemented by infrared orother means that does not affect the wafers.

Sensor 60 may also be implemented by coupling of transmitters andreceivers. As shown in FIG. 6, transmitters 61 transmit detectionsignals 63 to receivers 62. If transmitters 61 and receivers 62 arearranged horizontally to align all wafers, sensor 60 can furtheridentify and report a sliding wafer to control unit 1. As shown in FIG.10, a side view of an example of sensor 60 is provided. The closer thepath of detection signals 63 to wafers 13, the finer is the wafersliding detection ability of sensor 60.

When horizontal transmission robot 30 rotates to an orientation as shownin FIG. 3, wafers 13 are transferred from horizontal transmission robot30 to vertical transmission robot 40. Vertical transmission robot 40acquires wafers 13 when in a first orientation, and then verticallyrotates to a second orientation to make wafers 13 stand in a verticalorientation.

Normally, when vertical transmission robot 40 is in the secondorientation transporter 50 moves upward from its original position belowvertical transmission robot 40 to support wafers 13 in a verticalorientation, and moves wafers 13 along a specific track. Transporter 50can carry two lots of wafers, wherein wafers of a second lot areinserted between wafers of a first lot. Sensor 70 detects if any wafersdropped from vertical transmission robot 40 during the period from thebeginning of rotation of vertical transmission robot 40 to support ofwafers 13 by transporter 50.

Sensor 70 is disposed between vertical transmission robot 40 andtransporter 50 when vertical transmission robot 40 is in the secondorientation, and wafers 13 have not been supported by transporter 50.Sensor 70 may be fixed to transporter 50 or vertical transmission robot40, or even to another movable or stationary equipment or object.

Wafers 13 acquired by vertical transmission robot 40 are substantiallyparallel. The centers of wafers 13 substantially move along a verticalplane while vertical transmission robot 40 rotates from the firstorientation to the second orientation. Sensor 70 comprises at least onetransmitter dispatching a signal and one receiver accepting the signal.The transmitter and the receiver may be disposed on a fourth linesubstantially parallel to or lying on the vertical plane.

Control unit 1 determines that at least one of the wafers 13 drops ifthe signal from the transmitter to the receiver is interrupted during aperiod since wafers 13 are acquired by vertical transmission robot 40until wafers 13 are supported by transporter 50. Control unit 1 mayaccordingly stop transporter 50 when at least a wafer drops.

Sensor 70 may also be implemented by coupling of transmitter andreceiver. In a floor plan of sensor 70 as shown in FIG. 7, transmitters71 transmit detection signals 73 to receivers 72. If transmitters 71 andreceivers 72 align every wafer, sensor 70 can further identify andreport a dropping wafer to control unit 1. As shown in FIG. 8, a sideview of an exemplary sensor 70 is provided. Wafers 14 are waferspreviously acquired by transporter 50. Wafers 13 and 14 are interleavedon transporter 50.

A side view of another exemplary sensor 70 is provided in FIG. 9. FIGS.8 and 9 are side views of examples of sensor 70 in different directions.Under a condition when wafers 14 have been disposed on transporter 50,control unit 1 determines that at least one of the wafers 13 has droppedif the detection signals from transmitter 71 to receiver 72 areinterrupted during a period since vertical transmission robot 40acquires wafers 13 until wafers 13 and wafers 14 are interleaved.Control unit 1 may accordingly stop transporter 50.

Control unit 1 detects wafer sliding or dropping events utilizingsensors 60 and 70. When a wafer slide or a wafer drop event is detected,control unit 1 stops equipment carrying wafers and equipment acquiringthe wafers and restarts the stopped equipment when problems caused bywafer sliding or wafer dropping are addressed, thus wafer damage causedby a small number of sliding and dropping wafers is prevented.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A displaced wafer detection system, comprising: a unified podenclosing a plurality of wafers in a first position; a pod openeropening the unified pod; a horizontal transmission robot carrying thewafers from the unified pod to a second position; and a sensor, when oneof the wafers has reached the second position, detecting if any waferhas slipped during wafer transmission from the unified pod.
 2. Thesystem as claimed in claim 1, wherein the sensor is disposed between thehorizontal transmission robot and the pod opener while the wafers arecarried by the horizontal transmission robot from the unified pod to thesecond position.
 3. The system as claimed in claim 2, wherein the sensoris fixed to a first surface of the pod opener, and, when the horizontaltransmission robot carrys the wafers from the unified pod, the firstsurface faces the horizontal transmission robot.
 4. The system asclaimed in claim 2, wherein the sensor comprises at least onetransmitter dispatching a signal and one receiver accepting the signal,the wafers carried by the horizontal transmission robot aresubstantially parallel, when no wafer slips while being carried from theunified pod, the centers of the wafers reach and lie on a second line,the transmitter and the receiver are both disposed on a third line alongwhich the signal is transmitted from the transmitter to the receiver,and the third line is parallel to the second line.
 5. The system asclaimed in claim 4, wherein the wafers when being in the opened unifiedpod have the centers thereof substantially lie on a first line, and thesignal travels along a path on the same plane as the first and secondlines.
 6. The system as claimed in claim 4, further comprising a controlunit determining that at least one of the wafers slips when one of thewafers has reached the second position while the receiver does notreceive the signal.
 7. The system as claimed in claim 4, wherein thecontrol unit stops the horizontal transmission robot when at least oneof the wafers slips.
 8. A displaced wafer detection system, comprising aunified pod enclosing a first lot of wafers in a first position; a podopener opening the unified pod; a horizontal transmission robot carryingthe wafers from the unified pod; a vertical transmission robot, when ina first orientation, acquiring the wafers and then vertically rotatingthe wafers to a second orientation; a transporter moving upward tosupport the wafers in a vertical orientation when the verticaltransmission robot is in the second orientation; and a sensor detectingif any wafer drops from the vertical transmission robot before thewafers are supported by the transporter.
 9. The system as claimed inclaim 8, wherein the sensor is disposed between the verticaltransmission robot and the transporter when the vertical transmissionrobot is in the second orientation, and the transporter has notsupported the wafers.
 10. The system as claimed in claim 9, wherein thewafers acquired by the vertical transmission robot are substantiallyparallel, the centers of the wafers substantially move along a verticalplane while the vertical transmission robot rotates from the firstorientation to the second orientation, the sensor comprises atransmitter dispatching a signal and a receiver accepting the signal,and the transmitter and the receiver are disposed on a linesubstantially parallel to the vertical plane.
 11. The system as claimedin claim 10, wherein the transmitter and the receiver are substantiallydisposed on the vertical plane.
 12. The system as claimed in claim 10,further comprising a control unit determining that at least one of thewafers has dropped if the signal from the transmitter to the receiver isinterrupted during a period since the wafers are acquired by thevertical transmission robot until the wafers are supported by thetransporter.
 13. The system as claimed in claim 12, wherein the controlunit stops the transporter when at least one of the wafers drops. 14.The system as claimed in claim 12, wherein the transporter has had asecond lot of wafers disposed thereon, and the control unit determinesthat at least one of the wafers has dropped if the signal from thetransmitter to the receiver is interrupted before the first lot ofwafers and the second lot of wafers are interleaved.
 15. The system asclaimed in claim 14, wherein the control unit stops the transporter whenat least one of the wafers drops.
 16. The system as claimed in claim 8,wherein the horizontal transmission robot carries the wafers from theunified pod to a second position; further comprising: a second sensor,when one of the wafers has reached the second position, detecting if anywafer has slipped during wafer transport from the unified pod.
 17. Thesystem as claimed in claim 16, wherein the sensor is disposed betweenthe horizontal transmission robot and the pod opener while the wafersare carried by the horizontal transmission robot from the unified pod toa second position.